Valve



Nov.23,1954

Original Filed March 50, 1944 J. B. BROWN VALVE is Sheets-Sheet 1 /N VEN T 01? 5.55 5. ZSWOW/V ATTOR/VD NOV. 23, 1954 J, 3, BROWN 2,695,035

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k wM 0 y m5 5 \a g NQ J 5 #3 mm W\ W A TTORNAY United States Patent VALVE Jesse B. Brown, South Bend, Ind, assignor to Bendix Aviation Corporation, South Bend, Ind., a corporation of Delaware Continuation of abandoned application Serial No. 744,070, April 26, 1947, which is a division of application Serial No. 525.56%, March 36 194-4. Divided and this application Woveinher 2%, 1?52, Serial No. 322,935

11 Claims. (Cl. 137-622) This invention relates to hydraulic control devices and more particularly to valves.

This application is a continuation of my copending application Serial No. 744,070, filed April 26, 1947 now abandoned, the latter of which is a division of my copending application Serial No. 528,698, filed March 30, 1944, now Patent 2,432,721.

An important object of the invention resides in the provision of a novel valve for use in a hydraulic power steering system.

An object of the invention concerns a valve of the type having two members arranged .in a neutral position in which communication is established between the ports and from which position one of said members is movable in either direction to control flow characterized by two fiexible walls carried on one member and two valve seating elements carried by the other member for engagement respectively with the flexible walls.

Another object of the invention resides in the provision of a valve having a neutral position in which flow is established between all the ports and movable in either direction therefrom to disestablish flow between certain of the ports, whereby a difierential pressure is developed in the valve tending to restore the same to its neutral position.

Another important object of this invention is to provide a steering valve adapted to equalize the fluid pressure on the system at times when steering is not required.

Other objects and advantages of the hydraulic steering system will become apparent to those skilled in the art from a study of the drawings and description to be presently set forth.

In the drawings:

Figure l is a diagrammatic view of the remote control hydraulic steering system of this invention applied to the steering wheels of a vehicle;

Figure 2 is a longitudinal sectional view in elevation of the steering valve of the system shown in Figure 1;

Figure 3 is a view in section taken on the line 3-3 of Figure 2;

Figure 4 is a section taken on the line 44 of Figure 3 showing the valve member centering springs;

Figure 5 is a longitudinal sectional view of the steering valve of this invention showing the relative position of the parts upon rotation of the steering wheel; and

Figure 6 is a horizontal section of one of the control valves 23 of Figure 1 shown associated with other parts of the system.

The remote control hydraulic steering system of this invention is shown in Figure l and includes a motor unit 16 comprising a cylinder 12 having a reciprocable piston 14 disposed therein. The motor unit iii has integral therewith, a bracket 13 provided with a hole 13:: adapted to receive a pin, not shown, for pivotally securing the cylinder to a vehicle or machine so that full movement of the piston may be accomplished. A steering valve 16 is connected to a pump 18 through conduits 29 and 22. The pump 18 may be driven by the engine of the vehicle, not shown, or operated independently of said vehicle engine. Flexible conduits 24 and 26 connect the steering valve to the opposite ends of the cylinder 12, each conduit being provided with a control valve 28. The piston 14 is secured to a piston rod 3t) which actuates a lever 32, a reach rod 34 and a lever .36 to thereby move a pair of wheels or steered members 38 as shown in the present embodiment of the invention. However, it must be rec ognized that the actual ground engaging means or steered members may be any of the well-known type depending upon the application and that it is not intended to limit the use of the system to that type of steered members illustrated. A linkage, comprising a rod 40 pivotally connected to one end of a transverse lever 42 fulcrumed at 44 and having a cam 46 at its other end, connects the piston rod 30 to control valves 28 to thereby actuate said valves in accordance with the movement of the piston from its neutral or central position.

It is imperative to the operation and function of the system of this invention to provide a means that will tend to choke the flow of fluid pressure to one side of the piston and allow the fluid to escape unimpeded from the other side thereof in response to movement of the steering wheel. This enables the operator of the vehicle to exercise greater control over steering since each turn of the steering wheel will move the wheels at predetermined amount only, dependent upon the force exerted on the steering wheel by the operator. If continued turning of the vehicle wheels is desired the steering wheel must be rotated in the conventional manner. The means which I provide for performing this function comprises a pair of control valves 28. This arrangement, which as pointed out hereinafter is adapted to supply a reactionary force opposed to continued movement of the piston, enables the vehicle to be steered in increments and insures a positive control over the vehicle. Since the control valves 28 are identical only one will be described. The valve comprises a body portion 48 having an opening 50 communicating with the cylinder 12. A valve housing 52 threadedly engages the body portion 48 and is provided with an interiorly threaded portion 54 adapted to receive the conduits 24 or 26 to connect the steering valve 16 with one or the other of control valves 28. The valve housing has an integral prolongation 56 extending into the body portion 48 beyond the opening 50 which communicates with the cylinder 12. A valve element 58 having a passage 60 therethrough is slidably disposed in the housing 52 and normally biased to closed position, against a seat 59 formed in said housing, by a spring 62 to thereby orevent at times the passage of fluid to said cylinder. Radial openings 64- are circumferentially spaced about the valve housing to permit fluid under pressure to enter the cy inder from the control valve when the valve element 58 is in an open position. The passage 60 is enlarged at 66 to receive a spring 68 adapted to hold a ball check-valve 70 against a seat 72 formed at the junction of the enlarged assage 66 and passage 60. The ball check-valve permits fluid from the interior of the cylinder 12 to esca e throu h the passages 60 and 66 to the system but not vice versa. A push pin 74 having a circular plate portion '76 slidable in the body 48 is guided by a bearing portion 78 inte ral with the body 48. The push pin 74 is actuated by the cam 46 which forces the valve element 58 toward its seat 59 with a force the magnitude of which is dependent upon the rotation of the cam the rotation of the cam being dependent upon the displacement of the ist n from its n rmally central position.

For stee ing the vehicle to which the hydraulic steering system of this invention is connected, a steering valve 16 is provided. This valve includes a body portion 80 having a longitudinal bore 82 reduced at 84 and 86 for a pur ose to be presently described. The reduced portion 86 has a bearin 88 secured therein adapted to receive a steering shaft 90 having an intermediate threaded portion 91. To one end of the shaft is keyed, at 92, a steering wheel 94. It should be noted that the threads of the threaded portion 91 have such a lead that any axial force applied to the shaft at the end opposite the steering wheel will cause rotation of the steering wheel. in the present embodiment a triple thread is provided to obtain the desired results. The ends of the valve are sealed by caps 96 and 98 secured to the body 84 in any suitable manner such as by bolts 1% and 102 respectively. Cap 93 also provides a second bearing member 104 for the steering shaft 98. An annular recess 106, in the cap 93 is adapted to receive an oil seal 108 which retains the oil in the bore 82. An integral pilot-like extension 110 of the cap 98 protrudes into the bore 82 and provides an abutment for a Washer 112 which is urged against the extension 110 by a spring 114. A washer 116 engages the other end of the spring and abuts the shoulder formed by the reduced portion 84 of the bore. An interiorly threaded sleeve member or nut 118, having a flanged portion 128 and an exteriorly threaded portion 122, engages the intermediately threaded portion 91 of the steering shaft 90. A collar 124 threadedly engages the sleeve portion 122 and is locked thereto by set screw 126 which passes through a slotted portion 128 of the collar. The sleeve member 118 is provided with a keyway 136 and the body 88 with a keyway 131 adapted respectively to cooperate with keys 132 and 133 which are integral parts of the washer 112. This keyway arrangement insures axial or longitudinal movement of the sleeve 118 with respect to the steering shaft 90 and prevents the sleeve from revolving with the steering shaft when the steering Wheel is rotated.

For controlling the flow of fluid under pressure from the source to the steering mechanism the steering valve 16 embraces a valve assembly 134 disposed between the body 88 and cap 96, having a member 136 nested therein and adapted for slight axial movement. Assembly 134 is removably secured between the cap 96 and body portion 80 by the bolts 188. The illustrated embodiment of valve member 134 comprises sections 134a, 1341) and 134%- in juxtaposition, which include respectively a cylinder port 135, an inlet port 137 and outlet port 138, and a cylinder port 139. Axially and circumferentially spaced relative to the member 136 are valve seat engaging elements or discs 148 and 141 secured between section 1154b and sections 134a and 1340 respectively, adapted to cooperate with annular members 142 and 143 of the member 136 to thereby regulate the flow of fluid from the inlet to the outlet and/or to the cylinder ports. The annular members 142 and 143 form valve seats or faces 142a, 1425; and 143a, 143b respectively. The elements or flat rings 148 and 141 which are preferably made of a resilient or flexible material such as spring steel, form partitions separating the inlet 137 from the cylinder ports and from the outlet except that communication to these ports is at times provided through passages 146 and 147 when the member 136 is axially centered with respect to the valve member 134. When the member 136 is moved to an extreme right position, as shown in Figure 5, the face or valve seat 1431) is adapted to seat against an annular seating surface 145 of the section 1340. In this position face 1421) engages the valve seat engaging element 148. An extreme left position of the member 136 will cause the face or seat 142a to seat against the annular seating surface 144 of the section 134a; and face 143a engages the valve seat engaging element 141. Passages 148, 149, annular passage 158 and passage 151 connect the cylinder port 139 to outlet port 138. Likewise passages 152, 153, annular passage 154 and passage 155 connect the cylinderport 135 to outlet port 138.

The member 136 which extends axially of shaft 98 is engaged at its ends by a pair of substantially flat circular elements 156 which elements extend radially from member 136 and are adapted to engage the valve member 134. A frictionless element or thrust bearing 158 is secured between shoulder 168 of the shaft 98 and the element 156. A second thrust bearing 158 near the end of the shaft 90 is disposed between one of the elements 156 and a lock nut 162. The lock nut 162 is adapted for axial adjustment on the shaft to secure the bearings 158 into frictional engagement with the elements 156 and with the shoulder 160 and collar 162 respectively. This bearing arrangement permits free rotation of shaft 90 with respect to member 136, but any axial displace ment of the shaft results in a like movement of member 136. The sections 134a and 134s are recessed at 164 and 166 respectively, for the reception of the elements 156.

For centering the member 136, as shown in Figures 2 and 4, so that the passages 146, 147, 149 and 153 will have the same cross-sectional area eight springs 168 are provided. At this time, when member 136 is centered there will be an equal amount of fluid passing from the inlet 137 through the passages 146 and 147 respectively. The springs 168 are radially disposed relative to the steering shaft axis in apertures 170 and 172 of sections 134a and 134c respectively, and are suited to engage the elements 156 to thereby urge member 136 to a neutral or central position. The four springs 168 which act together on one of the elements 156 are weaker than the spring 114 which acts on the sleeve member 118.

The valve used herein is known in the art as an open center valve. The valve has a normally neutral position in which it permits a continuous flow of fluid from the inlet to the outlet through a plurality of paths.

Since the resistance offered to steering in systems of the remote control type is not transmitted to the steering wheel controlled by an operator, some means should be provided whereby an artificial feel of the car is communicated to the operator so that steering will seem more natural. Without feel the steering wheel has a disjointed feeling such as would be experienced if a steering wheel connected to a strictly manually operated vehicle were disconnected from the steered members. This feel is obtained in the valve of this invention by the spring 114 which is adapted to load the shaft 98 through the sleeve 118 and threaded portion 91 of the shaft. The greater the angular displacement of the steering wheel the greater the deflection of the vehicle wheels and the greater the effort demanded of the operator to turn the steering wheel.

Operation of the steering valve is as follows:

Any slight initial movement of the steering wheel, by the operator to his right, turns the shaft in the sleeve member 118 and at the same time tends to move the shaft 98 axially to the right as viewed in Figure 2. Continued rotation of the wheel in the same direction will shift the shaft axially to the right to thereby cause the member 136, including the valve seats 142 and 143, to be moved to the right. Movement of member 136 changes the areas of the passages 146, 147, 149 and 153 with a consequent change in fluid flow through these passages. A shift to the right of member 136 will enlarge the passage 146 to thereby increase the flow of fluid to the cylinder port 139, and will reduce the passage 147, to thereby decrease the fiuid flow to cylinder port 135. Simultaneously the passage 149 is reduced in area to thereby impede the flow of fluid pressure to the outlet 138 and the passage 153 is expanded to allow a greater amount of fluid to pass to the outlet 138. This movement of member 136 in an axial direction is against the four springs 168 disposed in section 134:: acting on the element 156. It should be noted that although the shaft 90 rotates and moves axially about its own axis the member 136 is urged in an axial direction only. The frictionless elements 158, which are interposed between the shoulder of the shaft 90 and the lock nut 162, convert the rotational and axial movement of the shaft 90 into strict axial movement of member 136. Movement of member 136 to the right compresses the springs 168 in section 134a. Continued movement of shaft 90 to the right against springs 168 builds up additional force in the springs acting axially on the shaft tending to urge it to the left. However, the force built up by compressing springs 168 is only slight and is intended primarily to return member 136 to its central position when the steering valve is not being used. Obviously any shift to the left of sleeve member 118 caused by rotational and/or axial movement of shaft 90 will carry with it the washer 116 which will cause spring 114 to compress, that is, the spring will be loaded. The position assumed by the parts of valve 16 when the steered members 38 are turned to the right is best shown in Figure 5. Where there is an axial thrust applied to shaft 90 as through axial movement of member 136, rotational as well as axial movement is imparted to shaft 90; that is, if the steering wheel is released strict axial movement of member 136 is converted into rotational and axial movement of shaft 90 which threads the nut 118 onto the shaft. However, if the steering wheel is held against rotation, any axial thrust of shaft 98, caused by axial movement of member 136 in response to a re actionary force transmitted to said member, will only shift the shaft axially against the load spring 114. it can be readily observed that as the reactionary force acting on member 141) becomes larger, spring 114 is compressed to a greater degree. This increased loading of spring 114 will necessitate greater effort by the operator to continue rotation of the steering wheel in the direction initiated.

Operation of the remote control hydraulic steering system is as follows:

Assuming a condition at any instant when the vehicle wheels are aligned so as to cause the vehicle to steer straight ahead, the position of the piston 14 and levers connecting the vehicle wheels will be as shown in Figure 1. For the position of the parts of the steering valve and control valve at this time see Figures 2 and 6 respectively. At this instant, that is, with the valves in the position shown in Figures 2 and 6, the fluid admitted to the inlet 137 divides equally between the two parallel paths formed by passages 146, 149, 150, 151 and 147, 153, 154, 155 respectively. These two paths are reunited at the outlet 138 where the fluid pressure returns unimpeded to the pump. Obviously with this relationship of passages, where there is an equal passage of fluid, there is a balanced condition of member 134. Under balanced conditions the pump 18 is only circulating the fluid through the steering valve 16 and the conduits 20 and 22.

Should the operator of the vehicle or dirigible machine wish to negotiate a turn to the right, that is, deflect the steered members 38 to the right, as viewed in Figure l he will only have to rotate the steering wheel 94 to his right. Rotation of the steering Wheel to the operators right, as previously described in the operation of the valve, produces an axial displacement of member 136 to the right. Axial displacement of the member 136 disturbs the equality of flow through the passages 146 and 147. In the instant example where the displacement of member 136 is to the right as best shown in Figure 5, passage 146 is enlarged to permit increased flow to the right side of piston 14 and passage 147 is reduced to 0bstruct the flow of fluid to the left side of piston 14. However, passage 153 is made greater to allow the flow of fluid from the left side of piston 14 to the outlet with a mini mum amount of obstruction. Passage 149 is constricted to prevent the increased flow to the cylinder port 139 from by-passing to the outlet 138. This increased flow to the right side of the piston 14 is through conduit 24, past the valve element 58 and radial openings 64. The flow to the right end of cylinder 12 will effect movement of the piston to the left to thereby deflect the vehicle wheels and actuate the push pin 74 of the control valve on the right which is connected to conduit 24. Actuation of push pin 74 compresses a spring 62 which urges valve element 58 against valve seat 59 to increase the resistance to the flow of fluid to the right end of cylinder 12. This resistance to flow is proportionate to the displacement of the piston from its center or neutral position. Increasing the resistance to the flow through the control valve as aforementioned causes a reactionary force to be built up in conduit 24 acting in a direction opposing the flow of fluid from cylinder port 139. This reactionary force is transmitted to the member 140 where it acts on the valve seat 142 tending to restore the member 136 to a balanced condition. As already explained movement of the member 136 axially by an axial force applied thereto is converted into rotational movement of the steering wheel whereby the wheel may be turned to its initial position. If it is desired to deflect the vehicle wheels further after the control valve has closed against the flow of fluid it will be necessary to apply a greater force than before to the steering wheel to cause additional movement of the member 136. To prevent excessive pressures in cylinder ports 135 and 139 pump 18 is provided with a built in conventional type relief valve, not shown, for relieving pressures above a predetermined value.

It is evident that as the reactionary force acting to restore the valve to balanced condition increases, the force applied at the steering wheel by the operator must also increase if a further turning of the vehicle wheels is desired.

For purpose of exemplification only the operation and function of the steering system was explained for executing a right turn. For accomplishing a left turn the steering wheel would be rotated to the left. The principles and function of operation are the same whether turning right or left.

Although the form of embodiment of the invention herein disclosed is the preferred form, it is to be understood that other forms might be adopted, coming within the scope of the appended claims.

I claim:

1. A valve of the character described comprising a body member having a bore therein, an inlet and two working ports in the body member, a valve member in the bore, said valve and body members having cooperating annular channels and passages to provide for flow between the ports and including an annular inlet port channel and two working port channels, one on each side of said inlet port channel, said members having a neutral position with respect to each other wherein communication is established between the ports and from which the members are relatively movable for controllmg communication between the ports, a flexible wall located between the inlet port channel and each of the working port channels and carried on one of the members, the other of said members being equipped with two valve seats axially spaced apart thereon for engagement respectively with the flexible walls, relative movement of said members from their neutral position to effect engagement between one of said valve seats and its associated flexible wall establishes a differential pressure across said wall which acts thereon tending to restore the members to their neutral position, and means for producing relative movement of said members from their neutral position.

2. A valve of the character described comprising a body member having a bore therein, an inlet and two working ports communicating with the bore, a valve member in the bore, said members having a neutral position with respect to each other wherein communication is established between the ports, said valve and body members having cooperating annular channels and passages to provide for flow between the ports and including an annular inlet port channel and two working port channels, one on each side of said inlet port channel, two flexible walls carried by one of the members, one flexible wall being located between the inlet port channel and one of the working port channels and the other flexible wall being located between said inlet port channel and the other of the working port channels, the other of said members being provided with two valve seats axially spaced apart thereon for cooperation respectively with the flexible walls for controlling flow between the ports, and means for producing relative movement of said members from their neutral position to effect movement of one of the valve seats toward its associated flexible wall to thereby establish a differential pressure across said wall which acts thereon tending to restore the members to their neutral position.

3. A valve of the character described comprising a body member having a bore therein, an inlet and two working ports in the body member in communication with the bore at axially spaced locations therein, a valve member in the bore, two flexible walls carried by one of the members and spaced apart axially thereon, and two valve seats carried by the other member and spaced apart thereon for engagement respectively with the flexible walls, said flexible walls and valve seats together providing annular channels with which the respective ports communicate, said'members having a neutral position with respect to each other wherein communication is established between the ports via said channels and from which position the members have relative movement for controlling communication between the ports, relative movement of the members from their neutral position eflects engagement between one of the valve seats and its associated flexible wall to thereby establish a differential pressure across the wall tending to restore the members to their neutral position, and means for producing relative movement of said members from their neutral positions.

4. A valve of the character described comprising a body member having a bore therein, inlet, outlet, and

' two working ports in the body member, a valve member in the bore, said members having cooperating annular channels and passages to provide for flow between the ports via said channels and including two annular working port channels communicating respectively with the two working ports, two flexible walls carried by one of the members and spaced apart axially thereon, and two valve seats carried by the other member and spaced apart axially thereon for seating respectively with the flexible walls, one of said flexible walls and its associated valve seat forming one side of one of the working port channels and arranged to control flow between the inlet port and the working port communicating with said one working port channel, the other of said flexible walls and its associated valve seat forming one side of the other of the working port channels and arranged to control flow between the inlet port and the working port communicating with said other working port channel, said members having a neutral position with respect to each other wherein communication is established between the ports via said channels and from which position the members have relative movement to establish a differential pressure across one of said flexible walls and its associated valve seat tending to restore the members to their neutral position.

5. A valve of the character described comprising a body having a bore therein, inlet, outlet, and two working ports in the body, said bore being formed with annular channels therein located at axially spaced intervals, one channel for each of the inlet and two working ports and two channels for the outlet port, means establishing communication between the ports and the respective channels, two valve seats carried by the body and arranged in the bore at axially spaced intervals, one of the two valve seats being located between one of the channels which communicates with the outlet port and a channel which communicates with one of the two working ports and the other of the valve seats being located between the other channel which communicates with the outlet port and the other channel which communicates with the other working port, a valve element in the bore movable in either direction from a neutral position, means holding said valve element in its neutral position, a pair of flexible ring members located in the bore transversaliy thereof and at axially spaced locations, said two valve seats and said two flexible members being arranged concentrically of said valve element, said members being carried by the body and located in the bore between the channel which communicates with the inlet port and each of the channels which communicate respectively with the working ports, said valve element having axially spaced valve seats formed for engagement with said flexible members and said two valve seats carried by the body, movement of the valve element in either direction from neutral first effects engagement with one or the other of said pair of flexible members and subsequent engagement with one or the other of said two valve seats in the body, movement of said valve element to a position where engagement with one of the flexible members is effected creates a differential in pressure across said one flexible member acting in a direction tending to restore said valve element to its neutral position, and means for moving said valve element in either direction from neutral.

6. A valve of the character described comprising a body having a bore therein, inlet, outlet, and two working ports in the body, said bore being formed with annular channels therein located at axially-spaced intervals, one channel for each of the inlet and two working ports and two channels for the outlet port, means establishing communication between the ports and the respective channels, two valve seats carried by the body and arranged in the bore at axially-spaced intervals, one of said two seats being arranged between one of the channels which communicates with the outlet port and a channel which communicates with one of the working ports and the other of said two valve seats being arranged between the other channel which communicates with the outlet port and the other channel which communicates with the other working port, a valve element in the bore slidable in either direction from a neutral position, spring means acting on said valve element for positioning the same in its neutral position, a pair of flexible ring members located in the bore transversally thereof and axially spaced apart therein, said two valve seats and said two flexible members being arranged concentrically of said valve element, said members being supported by the body and located in the bore between the channel which communicates with the inlet port and each of the channels which communicate respectively with the working ports, said valve element being constructed and arranged with axially spaced valve seats for engagement with said flexible members and said two valve seats carried by the body, movement of the valve element in either direction from neutral first effects engagement with one or the other of said pair of flexible members and subsequent engagement with one or the other of said two valve seats in the body, movement of said valve element to a position where engagement with one of the flexible members is effected creates a differential in pressure across said one flexible member acting in a direction tending to restore said valve element to its neutral position, and means for moving said valve element in either direction from neutral.

7. A valve of the character described comprising a body having a bore therein, inlet, outlet, and two working ports in the body, a valve element in the bore movable in either direction from a neutral position to control flow of fluid between the ports, means holding said valve element in its neutral position, said valve element and body bore having cooperating annular channels and passages to provide for flow between the ports and including an annular inlet channel and two working port channels, one on each side of said inlet channel and adjacent thereto, said inlet and working port channels being separated by two flexible wall members supported by the body transversely of the bore and concentrically related to said valve element, said valve element being equipped with two valve seats axially spaced apart thereon for engagement with said flexible members, movement of said valve element into engagement with one of the flexible members establishes a differential pressure across said member which acts thereon tending to restore the valve element to its neutral position, and means for moving said valve element from its neutral position.

8. A valve of the character described comprising a body member having a bore therein, an inlet and two working ports in the body member in communication with the here at axially spaced locations therein, a valve member in the bore, yieldable Wall means carried by one of said members, two valve seats carried by the other member, said yieldable wall means being engageable with said two valve seats, rigid means carried by said one member, two additional valve seats carried by said other member, said rigid means being engageable with said two additional valve seats, said yieldable wall means, rigid means, and all of said valve seats together providing annular channels with which the ports communicate, said members having a neutral position With respect to each other wherein communication is established between all the ports via said channels, and from which position the members are relatively movable for controlling communication between the ports, relative movement of the members in one direction from neutral tends to establish engagement of said yieldable means and said rigid means with one of their associated valve seats, relative movement of the members in the other direction from neutral tends to establish engagement of said yieldable means and said rigid means with the other of their associated valve seats, and means for producing relative movement of said members from their neutral position.

9. A valve of the character set forth in claim 8 wherein the relatively movable members include differential areas subject to fluid pressure, the larger of which, upon relative movement of the members and engagement of valve seats with the cooperating yieldable wall and rigid portion is effected by a pressure differential caused by fluid flow tending to restore the relatively movable members to a neutral position.

10. A valve of the character described comprising a body member having a bore therein, an inlet, an outlet and two working ports in the body member in communication with the bore at axially spaced locations therein, a reciprocable valve member in the bore, yieldable means and rigid portions carried by one of the members, valve seat means carried by the other member which includes first axially spaced valve seats for engagement with the yieldable means, and second axially spaced valve seats for engagement with the rigid portions of the first mentioned member, said yieldable means, rigid portions and valve seats providing channels with which respective ports communicate, the members having a neutral position with respect to each other wherein communication is established between the ports via said channels and from which position the members have relative movement for controlling communication between the ports, initial relative movement of the members from their neutral position effecting engagement between one of the valve seats and an associated yieldable means, further relative movement of the members effecting engagement of another valve seat and one of the rigid portions, to thereby establish a differential pressure communicating with said working ports, and tending to restore the members to their neutral position, and means for producing relative movement of said members from their neutral position.

11. A valve member as set forth in claim 10 wherein the relatively movable members include differential areas, the larger of which, upon relative movement of said members and engagement of the valve seats with the cooperating yieldable means and rigid portion, is effected by the pressure diflerential tending to restore the relatively Number movable member to a neutral position. 1,176,212 2,095,560 References Cited in the file of this patent 2,296,622 UNITED STATES PATENTS 5 2311955 Number Name Date 701,754 Moran June 3, 1902 Number 10 Name Date Fulton Mar. 21, 1916 Vickers Oct. 12, 1937 Wehe Sept. 27, 1942 Merker Feb. 23, 1943 FOREIGN PATENTS Country Date France Feb. 23, 1943 

